The present invention relates to rotary compressors. More specifically, the present invention relates to a rotary compressor having impact surfaces adapted to reduce objectionable noise.
A rotary type of compressor as commonly used for refrigerators and air conditioners often generates high frequency noise. Indeed, some refrigerators use rotary compressors which show a strong almost pure tone noise of about 4 khZ. As the human ear is quite sensitive to noise at this frequency, such noise is quite objectionable.
Various methods of reducing rotary compressor noise have previously been considered.
One approach is to redesign the casing of the rotary compressor so as to reduce the sound radiation from it. The noise heard by the human ear results from the vibration of the casing which encloses the whole compressor structure. Modifying the sound radiation pattern is necessary for this approach. The radiation can be modified by changing the bending rigidity of the compressor, i.e., changing the casing thickness or adding stiffness to the casing. However, redesigning the casing is relatively expensive and is therefore undesirable.
Another way of attenuating the compressor noise is by controlling the compressor gas spectrum. Any resonator type of device built into the discharge port works as a mechanical filter. This may adversely effect the compressor efficiency depending on the structure of the resonator.
Other attempts to reduce the high frequency noise have included changes in orifice design, clearances, and root radii. These changes have been only partially successful and are somewhat disadvantageous in that they often reduce the efficiency of the compressor.
Although the above approaches at noise reduction have been somewhat useful, there remains a need for significantly and inexpensively reducing the objectionable noise from a rotary compressor without reducing the efficiency of the compressor.